Relay selector circuit arranged to simultaneously test a selected group of trunks



Jan. 4, 1949. H. E, GRIMES 2,458,262

RELAY SELECTOR CIRCUIT ARRANGED TO SIMULTANEOUSLY TEST A SELECTED GROUP OF TRUNKS Filed Jan. 50, 1946 @conm.

HARLAN E. GRIMES ATTOR NEY Patented Jan. 4, 1949 UN 1 TE D TSTATZETS PATENT OTFLFFICE.

'RELAY SELECTOR 'CIRCUIT ARRANGED T0 'SITVIULTANEOUSLY TEST A SELECTED GROUP "0F 'TRUNKS Harlan E. :Grimes, Bromley, Iludlow- Station, *Ky., assignor to Automatic Electric Laboratories, Inc., Chicago, Ill.,.a corporation ofDelaware Application January 30, IMGfS'eriaFNm 6441339 of :maintenance problems which results from the use of a minimum amount of Icommon equipment.

:Many systems *have been invented which use relays as the sole switching means, :the object being to reduce the degreeof .mainten'ance required to a minimum :and to simplify imainte name by reducing the number of types ofaswitching'mechanisms employed. In such all-rlay-ltelephone systems the advantages of the Strowger unit construction can easily be retained :in'asmall exchanges of several hundredlinesfordess. For larger systems it has heretofore been necessary to resort to common control circuits with "the attendant disadvantages of reduced reliability and increased maintenance difficulty due tothe complexity of the circuits. While =these..larger systems could theoretically employ all-relay selectors which would function .in an identical manner to the well-known Strowgerswitchesuch operation is considered impractical: as relay chains generallycannot hunt for-an idle trunk in ai'group thereof at ashigh a rate of speed: asa mechanical switch. Fast trunk hunting is essential :in a

step-by-step system to insure the extension of -:a

connection from one switch toran'id1eswitch'in2a succeeding group between the .dialingpf successive digits b the calling subscriber.

It is accordingly an :object 'Jof'the presentinventicn to provide a self-contained relayetype selector which is arranged to test allxtrunksrina selected group simultaneously and to establish connection with an idle one thereof.

The invention has'been illustratedx'in theiform of a schematic diagram in the accompanying drawing. It comprises aselector'havin'g "a plurality of group selecting (tens) relays each of which is operative to i connect an associated group -.of trunks to a group of individual selecting (units) relays. A group of controlrelays an-dan'impulse counting device-areprovided' for selectively operating the group selecting relays .in accordance with a series of digital impulses received over a calling subscribers line. When adesired :one of the group selecting relays :has .been operated, the individual selecting relays test all oi 'the trunks in the selected group simultaneously and extend the calling line to an idle one thereof.

Referring now to the drawing, there vis illustrated a calling subscribers substation A:which is connected to'the incoming'conductors Ll, 1L2

andC of the selector via a line switch,-.or the equivalent, shownin block form. Following conzventiona'l step-.to-tsteppractice, the selector has access .toatengroupsof trunks, each group including ten trunks. :Eachtrunk terminates'in a con- :nectortoi which-one'isshown in block form. Each connector usually-has access to Ionehundredsub- :scribers :lin'es,;a1l-;of the connectors .in a 'group :having access to'the same lines.

When a subscriber at substation --A"'raises.the handset from the hookswitch to initiate a call,

"the-line switch searches :foran idle selector. As-

suming that the :selector illustrated .is rthe first idle one :found bythe line switch, it'extends the calling line to conductors Ll :andLZ :and extends ground-over conductor C. ThECOIlnBCtlOHOf the subscribers loop between conductors LI .and L2 causes rrelay rlilfl to operate and: close.- a circuit to relayd20at contacts Ill. The lground extended over conductor C completes a circuit through chain contacts, :such :as Ulc -onfrelays UI xtoUll;

off-normal contacts 1162; relay 1130,; and chain contacts, 'such as Ulb,-1-on relays =.U| to UO to batter-y. Relay #30 :operates and grounds asupervisory lead .at contacts 3| to-gprovide an alarm .in casedialing-does notcommence within a given time. Relay 21120 :operates and places a. multiple ground on conductor .Cvat :contacts IZI. +ground initially .extendedover this conductor .The

from the line switchlis subsequently removed.

.The operating ground for relay llfllis obtained over conductor 'IDTG which is connected .to

groundthrough a winding of adial tone transformer, notshown. .The dial tone is'transmitte'd .to the .calling party to indicatethat the exchange equipment is prepared to receive impulses. When the 'calling'subscrib'er operates the calling device ithe"circuititolrel ay I I 0 is interruptedianumber of times corresponding 'to'the first 'digit'oi the called partys'number. Each time that relay I'Hl restores it closes'a circuit from groundthrough contacts 1,103,122 and M2 tothe-'stepping"mag net Hill of the'minor-switch MS; 'and'closes a 'circuit from ground through contacts 142 and 1-23, relayl=30,'and contacts such as'Ul'b on relays UI to U0 to battery. The stepping "magnet l 60 advances the minor-switch *wipers WI and 'W2 one step each time "its circuit vis completed by zth'e-restoration of relay H0. On-the first-step I the off-normal 'contacts l l 62 and I 63 are operated. The contacts 162 open the initial-operating circuit to relay i t3!) "which is thereafter hel'd "byxthe intermittent:completion of its circuit at contacts 1 I 2. lBoth relays [-20 and I l'30-are renderedzslowto release by means of copper sleeves scrthat they will .remainoperat edidurin'g. impulsing.

..At':the en'd of'itheseriesfof impulses relay 'I'I-O will ;remain roperate'd, :thereby ":causing .frelay t [30 .to rrestoreafter .:a brief rdelay. 'when relayllilfl :restores it closesz'groun'd throughiwiper W2 .con-

tacts 4225 and 1:32, relay I51], .and contacts 581101). asU-lb on'relaysUl to "Ullito battery; "and .closes ground through wiper W2, contacts I33, and 1 wiper WI to the selected one of the tens relays TI to T0. Assuming that wiper WI had been advanced to the tenth step, relays T and I50" operate to extend the test conductors of trunks [H to 00 to the lower windings of relays UI to U0,

respectively, through contacts such as T00 and I If these trunks are in use the test conductors are grounded, but when. they are idle resistance battery is connected to the test conductor.

One side of the lower winding of relay UI is connected to ground through contacts I2I while the corresponding side of the lower windings of each of the succeeding relays U2 to U0 are connected i to the same ground through break contacts, such as tile, on each preceding relay. As there may be a number of trunks which are idle, several of the relays UI to U0 may operate simultaneously. The lowest numbered relay to operate will close a locking circuit to its upper Winding from ground through break contacts such as UIc on all of the preceding relays, its own make contacts such as U20, and break contacts such as UIc on all of the preceding relays to battery. The lowest numbered relay to operate opens the operating and locking circuits to all of the succeeding relays at contacts such as U and Uib, respectively. The operation of contacts such as U2?) also opens the circuit to relay I50 causing it to lrestores after a brief delay and removes a multiple ground from the control conductor C at contacts I2I (by this time the succeeding connector switch will have grounded the control conductor). The connection is extended to the called party B by the connector under the control of the calling party in'the usual manner.

When the conversation has been completed and the calling party disconnects, the connector removes ground from the test, or control, conductor of trunk 0I thereby opening the locking circuit to the upper winding of relay UI. Relay UI restores and opens the circuit to relay I00 at contacts Uia. Relay I00 restores; closes a circuit from ground through contacts III, I03, I22, I43

and IE3 to the minor switch release magnet IBI;

and closes ground through wiper W2, contacts I and I04, and the upper winding of relay I30. The battery for energizing the release magnet IOI and the upper winding of relay I is connected in series with a common supervisory relay not shown. The release'magnet operates over the above circuit to permit the minor switch wipers to restore to normal. Relay I30 operates and closes ground to the common supervisory equipment at contacts I3 I. During the time that the minor switch MS is restoring the selector is guarded by preventing battery through contacts such as UIb and the lower winding of relay I30 from being impressed on the C conductor at contacts I62. When the minor switch has restored completely the latter contacts are closed and contacts I83 open to interrupt the circuit to release magnet IOI. At the same time the circuit to the upper Winding of relay I 30 is opened at wiper W2 permitting it to restore.

In the event that all of the trunks in the 0 group were busy at the time that relay I50 was operated following the termination of the series of impulses received over the calling line, none of the relays UI to U0 will be operated. When relay I50 operated it closed a circuit from ground through contacts I52, relay I40, and contacts such as Ulb on relays UI to U0 to battery. Relay I40 is made slow to operate by a copper slug on the armature end of its core to enable relays UI to U0 to operate first if any trunks are idle. After a brief delay relay I40 operates, provided none of the relays UI to U0 have operated; transfers the lower winding of relay I I0 from the dial tone and ground lead DTG to the busy tone and ground lead BTG at contacts I4I; opens points in the circuits to magnets I60 and IEI at contacts I42 and I43; closes a circuit from ground, through contacts I44, the lower winding of relay I30, and contacts such as UIb on relays UI to U0 to battery; locks to ground through contacts I24 at contacts I45; and grounds wiper WI at contacts I41 to hold relay T0 operated after I30 reoperates. Relay I30 operates and opens the circuit to relay I50 at contacts I32. Relay I50 restores, opens the operating circuit to relay I40 at contacts I52, and disconnects relays UI to U0 from the control conductors of trunks UI to 00 at contacts such as I5I. When the calling party hangs up in response to the busy signal, relay IIO restores and opens the circuit to relay I20 at contacts II I. Relay I20 subsequently restores, opens the locking circuit to relay I40 at contacts I24, closes ground through these contacts and contacts I40 and TM to the all trunks busy lead ATE-0 of the 0 groups of trunks, and closes ground through wiper W2 and contacts I25 and I04 to the upper winding of relay I30. Relay I40 restores after a brief delay, closes a previously traced circuit to the minor switch release magnet I 6| at contacts I43, opens the circuit to the lower winding of relay I30 at contacts I 44, removes ground from lead ATE-0 at I contacts I 46, and opens the circuit to relay T0 at contacts I41. Relay T0 restores and the minor switch and relay I30 restore in succession as previously described. The momentary ground on the ATE leads may be used to operate peg count meters for traffic study. a

In order to facilitate tracing calls, each of the group selecting relays TI to T0 is provided with contacts such as T0e for connecting lamp I10 to a corresponding one of the leads TL-I to TL--0. Thus by grounding lead TL0 the lamps, such as I10, of all selectors switched through to the 0 group of trunks will be illuminated.

While a particular embodiment of the invention has been illustrated, it should be understood that numerous modifications may be made therein without departing from the scope of the invention as defined in the subjoined claims; for example, the minor sWitch MS may be replaced by a relay type counting chain if desired.

What is claimed is: e

1. In a telephone system, a calling line, a plurality of groups of trunks each including a test conductor for marking them busy or idle, a plurality of group selecting relays, a plurality of individual selecting relays, means for selectively operating said group selecting relays in accordance with digital impulses received over the calling line, each of said group selecting relays operative to extend the test conductors of a corresponding group of said trunks to said individual selecting relays, said individual selecting relays operative to test all of the trunks in the group extended thereto simultaneously and to extend said calling line to an idle one thereof.

2. In a telephone system as claimed in claim 1, time delay means started in operation when any of said group selecting relays are operated and stopped when any of said individual selecting relays are operated, said timing means operated to transmit a busy signal over the calling line in the event that none of said individual selecting relays are operated within a predetermined time interval following the operation of any of said group selecting relays.

3. In an automatic selector switch of the relay type, a plurality of group relays each adapted to establish connections simultaneously with a group of trunk lines, impulse responsive means directively controlled in accordance with a digit in a called number for selecting and energizing one of said group relays to select the associated group of trunk lines, and a plurality of individual trunk selecting relays operative to test all of the trunks in the selected group simultaneously and to establish connection with an idle one thereof in response to the operation of One of said group relays.

4. In a telephone system, a calling line, a plurality of groups of trunks each including a test conductor for marking them busy or idle, a plurality of group selecting relays, a plurality of individual selecting relays, means for selectively operating said group selecting relays in accordance with digital impulses received over the calling line, each of said group selecting relays operative to connect the test conductors of a corresponding group of said trunks to said individual selecting relays, said individual selecting relays operative to test all of the trunks in the group connected thereto simultaneously and to select an idle one thereof, and means responsive to the operation of any of said individual selecting relays for severing said connection of the test conductors of the selected group of trunks to the said individual selecting relays.

5. In an automatic selector switch of the relay type, a plurality of group relays each adapted to establish connections simultaneously with a group of trunk lines, impulse responsive means directively controlled in accordance with a digit in a called number for selecting and energizing one of said group relays to select the associated group of trunk lines, a plurality of individual selecting relays, means operated momentarily upon the selection of a group of trunk lines for connecting the test conductors thereof to said individual selecting relays, said individual selecting relays operated to test all of the trunk lines in the selected group simultaneously and to select an idle one thereof in response to the momentary connection of the test conductors thereto.

6. In an automatic selector switch, a plurality of individual selecting relays, a plurality of group selecting relays each arranged to connect a corresponding group of trunk lines to contacts of said individual selecting relays, a further relay arranged to connect the test conductors of a selected group of trunk lines to windings of said individual selecting relays, means responsive to a series of impulses for selectively operating one of said group relays and for momentarily operating said further relay upon the termination of the series of impulses, said individual selecting relays operative to test all of the trunks in the selected group simultaneously and to select an idle one thereof in response to the concurrent operation of one of said group relays and said further relay.

'1. In a telephone system, a calling line, a plurality of groups of trunks each including a test conductor for marking them busy or idle, a chain of relays, means for selectively extending said groups of trunks to said chain of relays in accordance with digital impulses received over the calling line, said chain of relays operative to test the test conductors of all of the trunks in the group extended thereto simultaneously and to extend said calling line to an idle one thereof.

8. In a telephone system, a plurality of selectors each having access to a plurality of groups of trunks, a plurality of conductors each corresponding to one of said groups, an indicating means for each selector, means in each of said selectors operated in response to the selection of one of said groups of trunks for connecting the corresponding one of said conductors to the indicating means of the selector, whereby all of the selectors which have selected a given group of trunks may be readily identified by completing a circuit to the conductor corresponding to the given group to energize the indicating means of such selectors.

9. In a telephone system, a calling line, a selector switch, a plurality of groups of trunks each including a test conductor for marking them busy or idle, testing means, means for selectively extending said groups of trunks to said testing means in accordance with digital impulses received by said switch over the calling line, said testing means operative to test the test conductors of all of the trunks in the group extended thereto simultaneously and to cause said calling line to be extended to an idle one thereof.

10. In a telephone system, a calling line, a selector switch, a plurality of groups of trunks, a progressively movable device for selecting desired ones of said groups of trunks in accordance with digital impulses received by said switch over the calling line, and testing means operated to test all of the trunks in a selected group simultaneously and to cause said calling line to be extended to an. idle one thereof.

11. In a telephone system, a calling line, a plurality of groups of trunks, a test conductor for each trunk, an automatic switch having group and units relays for extending connections, impulse responsive means for selectively operating any one of said group relays to prepare connections to all of the trunks in a selected one of said trunk groups, automatic means for thereupon connecting the test conductors of all of said last named trunks to said units relays to test all of such trunks simultaneously and to energize those units relays connected to idle trunks, and circuits controlled by said units relays to permit the operation of only one of such energized relays to extend a connection from said calling line to an idle trunk in the selected trunk group.

HARLAN E. GRID/IE8.

REFERENCES CITED e following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,593,387 Clark I- July 20, 1926 

